Simplify to lowest terms. $\dfrac{16}{20}$
Answer: There are several ways to tackle this problem. What is the greatest common factor (GCD) of 16 and 20? $16 = 2\cdot2\cdot2\cdot2$ $20 = 2\cdot2\cdot5$ $\mbox{GCD}(16, 20) = 2\cdot2 = 4$ $\dfrac{16}{20} = \dfrac{4 \cdot 4}{ 5\cdot 4}$ $\hphantom{\dfrac{16}{20}} = \dfrac{4}{5} \cdot \dfrac{4}{4}$ $\hphantom{\dfrac{16}{20}} = \dfrac{4}{5} \cdot 1$ $\hphantom{\dfrac{16}{20}} = \dfrac{4}{5}$ You can also solve this problem by repeatedly breaking the numerator and denominator into common factors. For example: $\dfrac{16}{20}= \dfrac{2\cdot8}{2\cdot10}= \dfrac{2\cdot 2\cdot4}{2\cdot 2\cdot5}= \dfrac{4}{5}$